1. Field of the Invention: The present invention relates to an aqueous composition of phosphated epoxy resins and non-self water-dispersible resins, and methods of making and using same. More specifically, the present invention relates to water-based coatings of the above compositions which have been found to be very suitable for can or coil coatings.
2. Brief Description of the Prior Art: Resinous blends containing acrylic and/or epoxy resins are generally known in the art. In a number of instances, the resinous blends are limited in their use as essential film-formers because of problems of incompatibility of the resins with one another or with the medium in which they are present. The problem of incompatibility results in less than the desirable stability of coating compositions of the blends and also results in less than the required film properties such as film continuity, flexibility, adhesion and other desirable film properties.
In the instance of water-based compositions, it is seemingly more problematic to prepare coatings comprising resinous blends having the afore-stated properties. On one hand, the resins are made compatible with water typically by the use of hydrophilic groups such as acid salt groups. Without the hydrophilic groups, the resin, seemingly, would be non-self dispersible in water. On the other hand, the hydrophilic groups may present a rather serious problem of less than the desirable film durability. In the area of can coatings in particular, the above problems are unacceptable. Coatings intended for use in food and beverage industries must meet stringent property requirements in order to be useful for this purpose. The coating must adhere well to the base metal and must possess a certain set of flexibility, extensibility and adhesion characteristics so as to withstand the processing of the container itself. The coating must also be able to resist heat which can be encountered during processing of the container. Additionally, the coating itself must not affect the taste of a food or beverage which is put into the coated container.
The present invention provides a means of employing resins that are not self-dispersible with a base in water, in combination with phosphated epoxy resins to produce a water-dispersible blend.